Method and apparatus for producing high purity calcium



H. A. TIMM Jan. 31, 1967 METHOD AND APPARATUS FOR PRODUCING HIGH PURI'IY CALCIUM Filed April 9, 1964 United States Patent-O 3,301,665 METHOD AND APPARATUS FOR PRODUCING HIGH PURITY CALCIUM Harold A. Timm, Westmeath, Ontario, Canada, assignor to Dominion Magnesium Limited, Toronto, Ontario,

Canada, a corporation of Canada Filed Apr. 9, 1964, SeraNo. 358,546 Claims priority, application Canada, Apr. 23, 1963, 873,873 7 Claims. (Cl. 75--67) This invention relates to the production of high purity Ca by reduction of lime with Al powder under vacuum at temperatures in excess of 1100 C.

A known method of producing Ca metal is by the heating of a compacted mixture of calcined lime and Al powder in a retort under vacuum to a temperature of from about 1150 to 120 C., driving off Ca vapour into a condenser where the vapour condenses into a Ca metal crown in the condenser sleeve. The vacuum is then broken, the sleeve removed and the Ca crown is knocked or pressed out of the sleeve.

The problem of the carry over into the crown of charge impurities, particularly Mg, having vapour pressures similar to or higher than Ca, has been recognized and various means for creating two or more temperature zones in the condenser for selective condensation have been used. The increasing demand for high purity Ca has emphasized the necessity of finding an improved solution to this prob lem particularly because lime having a suitably low Mg content is difficult to obtain.

The broad idea of using a bafiile or heat shield in a condenser to create two temperature zones for selective con-' densation is known but none of the known arrangements are entirely suitable for the subject application because of the difficulties involved in the removal of the rather soft Ca crown from the condenser sleeve.

Broadly this invention comprises an apparatus for the production of Ca by heating calcined lime and Al powder under vacuum at a temperature in excess of 1100 C. including a retort and a condenser, thecombination consisting essentially of a condenser sleeve and a separator plate unit, said unit standing self-supported within said sleeve at a distance equal to from 30 to 150% of the average diameter of said sleeve, from the hot end of sleeve and filling from 30 to 90% of the cross-sectional area of said sleeve. 2 r

The invention is described in association with the accompanying drawings in which:

FIGURE 1 is a side elevation in section of the combination of the present invention in place following condensation,

FIGURE 2 is an end view in section of the sleeve condenser and separator plate unit taken along line 22 of FIGURE 1 but before condensation,

FIGURE 3 is a partial sectional elevation view of a further embodiment of the invention.

In FIGURE 1 a furnace 1 has a retort 2 therein, fixed to a condenser 3 having a water jacket 4 therearound. Lid 5 is removably secured to the cold end of condenser 3 and is made vacuum tight as by rubber gasket 6. A vacuum may be drawn on the system as through conduit 7. The retort 2 is commonly made of thick walled alloy steel having an internal taper over the cool-end portion 8 thereof. The condenser 3 is commonly made of thinner walled alloy steel and is normally butt welded to the cool-end of the retort.

The removable preferably mild steel condenser sleeve 9 is inserted into the condenser 3 and pushed forward against the taper in the cool end portion 8 of the retort 2. A loose fitting plug 10 fitting into the cool end of the sleeve 9 may be used around which very high vapour ICC pressure impurities such as Na and K may leak to condense on the cool end of the condenser.

The separator bafile or unit 12 is preferably of mild steel of rectilinear configuration and in preferred form consists of two spaced substantially vertical plates, a hot plate 13 and a cool plate 14 and enclosing side walls 15. The cool plate 14 preferably has an aperture 16 therein for insertion of a long-handled hook tool used in handling and positioning the unit when it is warm.

In operation lid 5 is opened and a charge 17 of calcined lime and Al powder briquets is fed into the retort. The condenser sleeve 9 is inserted and pushed forwardly to closely engage the tapered portion 8 of the retort. The separator unit 12 is then positioned to stand self-supported in the sleeve 9 filling from 30 to 90% of the cross sectional area of the sleeve and at a distance from the hot end of the condenser sleeve equal to from .3 to 1.5 times the diameter of the sleeve. The plug 10 is inserted and lid 5 is closed and made vacuum tight. A vacuum of about 0.001 atmospheres is drawn on the system and e the furnace is fired to give a temperature of about 1150 to sealed by condensate to give efiicient separation.

1200" C. in the retort. Na and K impurities come off and pass right through plug 10 to condense on the cold end of the condenser. The water jacket is operated to maintain the temperature at not more than 650 C., on the cold side of the separator unit 12 and at about 700 to 850 C.- on the hot side. The Mg tends to pass the separator unit and condense on the cold side thereof in high Mg crown 18 while the Ca tends to condense on the hot side in high Ca crown 19.

When the charge is spent the vacuum is broken, lid 5 removed, plug 10 withdrawn and condenser sleeve 9 is drawn out. After cooling in the air the Whole condensate body is pressed out of the hot end of the condenser sleeve. The higher the purity of the Ca crown the softer I it is and the more difiicult to press cleanly from the sleeve.

However in the present invention the presence of the relatively hard and brittle high Mg crown around the outside and the central separator unit assists greatly in achieving an easy, clean press of the condensate from the sleeve. The brittle high Mg crown 18 chipped away and the separator unit removed leaving the high Ca crown 19.

The process has been operated to obtain Ca having an average of only 0.25% Mg leaving a high Mg condensate containing 3.4% Mg. By moving the separator unit closer to the hot end of the sleeve Ca containing less than 0.1% Mg has been obtained.

The separator unit may conveniently be square or rectilinear in cross section so that the high Mg crown will be thin or broken at the four corners thereof and can be readily chipped off. The unit must be self-supporting and is preferably without legs or supports from which it will be difficult to separate the condensate. It can conveniently be about 2 /2 inches thick. If it is much thinner it will not easily stand by itself in the sleeve and if it is substantially thicker there will be a less distinct separation because most of the high Mg will condense around the edges and not beyond the cold face thereof.

If the unit fills more than of cross-sectional area of the sleeve the remaining gap tends to be too soon If it fills less than 30% it tends to be ineffective in creating sufiiciently sharp temperature zones. A preferred range is from 40 to 70% of the sleeve area and about 50% tends to be optimum for most purposes.

The positioning of the unit in the sleeve is partly dependent on the cooling system since the cold side must be at a temperature of not more than 650 C. and the hot side should be from about 700 to 850 C. in a zone large enough to receive all the Ca from the charge. Further, the hotter the hot side is the purer the Ca crown 'but the more Ca that passes intothe high Mg crown. Accordingly, in practise it can readily be determined for given equipment and a required Ca purity, where the optimum position of the separator unit is. Broadly the distance between the hot end of the sleeve and the hot face of the unit should be equal to from about 3-0 to 150% of the diameter of the sleeve and preferably from about 75 to 110% of the diameter of the sleeve. The length of the cold zone of the sleeve should be sufficient to condense all of the high Mg crown so that the plug will not get clogged. The length of the cold zone may conveniently be equal to from about 50 to 100% of the diameter of the sleeve.

The embodiment of FIGURE 3 is the same as that of FIGURE 1 except that the sleeve 9 is circumferentially split and consists of a pair of tubular members 20 and 21 axially aligned in end to end contacting relationship and the separator unit is positioned adjacent the contacting ends of said members. In this embodiment, when the sleeve is removed the two sections can be knocked apart and one will contain the high Ca crown and the other the high Mg crown. Each crown can then be pressed out of the ends which were in contact. It will be appreciated that were it not for the presence of the separator unit it would be quite difiicult to knock the two sections apart.

As an example of suitable dimensions and positioning, when the sleeve has a inch diameter the unit may conveniently be 6.5 inches square and 2 /2 inches thick composed of two /2 inch mild steel plates enclosed around their edges to contain a space 1% inches thick, the hot face of the unit being about 9 inches from the hot end of the sleeve and about 9 inches from the cold end of the sleeve.

What is claimed is:

1. Apparatus for the production of calcium which comprises the combination with a retort and a condenser, of a tubular condenser sleeve in said condenser, and a separator bafile seated in said sleeve and having a face disposed in substantially perpendicular relation to the axis of said sleeve, said face dividing the interior of said sleeve into a first section adjacent said retort and a second section remote from said retort, said face occupying 30 to 90% of the cross-sectional area of said sleeve, said first section having a length equal to from 30 to 150% of the average diameter of said sleeve, said second section having a length equal to at least 50% of the average diameter of said sleeve.

2. Apparatus for the production of calcium as defined in claim 1, said separator bafiie comprising a pair of spaced rectilinear plates and side walls fixed to and joining the peripheral portions of said plates, one of said plates having thereon said face, the other of said plates having a centrally disposed aperture therein.

3. Apparatus for the production of calcium as defined :in claim 1, wherein said face occupies 40 to 70% of the cross-sectional area of said sleeve, and wherein said first section has a length of from 75 to 110% of the average diameter of said sleeve.

4. Apparatus for the production of calcium which comprises the combination with a retort and a condenser, of a tubular condenser sleeve in said condenser, said sleeve having two axially aligned tubular sections in end to end contacting relationship, the first one of said sections adjacent said retort having a length equal to from 30 to 150% of its diameter, the second one of said sections remote from said retort having a length equal to at least 5 0% of its diameter, and a separator baflle seated in said sleeve adjacent the junction of said sections, said baflle having a face occupying 30 to of the cross-sectional area of said sleeve.

5. Apparatus for the production of calcium as defined in claim 4, wherein said first section has a length from 75 to of its diameter, and wherein said 'bafi le face occupies 40 to 70% of the cross-sectional area of said sleeve.

6. Apparatus for the production of calcium as defined in claim 5, said baffle comprising a pair of spaced rectilinear plates and enclosing side walls extending around the perimeters thereof, the thickness of said unit being about 2 /2 inches.

7. In the method preparing calcium by heating compacted calcined lime and aluminum powder in a retort at a temperature in excess of 1100 C. and under vacuum and condensing calcium in a condenser connected directly to the retort including the steps of collecting the calcium condensate in a condenser sleeve and subsequently pressing the calcium condensate out of the sleeve in the form of a calcium crown, the novel steps which comprise positioning a self-supporting separator unit in said sleeve filling from 30 to 90% of the cross-sectional area thereof at a distance from the hot end of said sleeve equal to from 30 to the diameter of said sleeve and at a dis tance from the cold end of said sleeve not less than 50% of said diameter, maintaining a temperature not greater than 650 C. on the cold side of said unit, and a temperature greater than 650 C. on the hot side thereof thereby forming a high calcium crown on said hot side and a high magnesium crown on said cold side subsequently pressing the condensate out of the sleeve and then chipping off the high magnesium crown and removing the separator unit leaving a calcium crown of high purity.

References Cited by the Examiner UNITED STATES PATENTS 2,650,085 8/1953 Burnett 26619 3,207,495 9/1965 Gibbs 26619 FOREIGN PATENTS 606,641 8/ 1948 Great Britain.

JOHN F. CAMPBELL, Primary Examiner.

R. F. DROPKIN, Assistant Examiner. 

7. IN THE METHOD PREPARING CALCIUM BY HEATING COMPACTED CALCINED LIME AND ALUMINUM POWDER IN A RETORT AT A TEMPERATURE IN EXCESS OF 1100*C. AND UNDER VACUUM AND CONDENSING CALCIUM IN A CONDENSER CONNECTED DIRECTLY TO THE RETORT INCLUDING THE STEPS OF COLLECTING THE CALCIUM CONDENSATE IN A CONDENSER SLEEVE AND SUBSEQUENTLY PRESSING THE CALCIUM CONDENSATE OUT OF THE SLEEVE IN THE FORM OF A CALCIUM CROWN, THE NOVEL STEPS WHICH COMPRISE POSITIONING A SELF-SUPPORTING SEPARATOR UNIT IN SAID SLEEVE FILLING FROM 30 TO 90% OF THE CROSS-SECTIONAL AREA THEREOF AT A DISTANCE FROM THE HOT END OF SAID SLEEVE EQUAL TO FROM 30 TO 150% THE DIAMETER OF SAID SLEEVE AND AT A DISTANCE FROM THE COLD END OF SAID SLEEVE NOT LESS THAN 50% OF SAID DIAMETER, MAINTAINING A TEMPERATURE NOT GREATER THAN 650*C. ON THE COLD SIDE OF SAID UNIT, AND A TEMPERATURE GREATER THAN 650*C. ON THE HOT SIDE THEREOF THEREBY FORMING A HIGH CALCIUM CROWN ON SAID HOT SIDE AND A HIGH MAGNESIUM CROWN ON SAID COLD SIDE SUBSEQUENTLY PRESSING THE CONDENSATE OUT OF THE SLEEVE AND THEN CHIPPING OFF THE HIGH MAGNESIUM CROWN AND REMOVING THE SEPARATOR UNIT LEAVING A CALCIUM CROWN OF HIGH PURITY. 